This disclosure relates generally to an audio system in an eyewear device, and specifically relates to an optical microphone for use in eyewear devices.
Head-mounted displays in an artificial reality system often include features such as speakers or personal audio devices to provide audio content to users of the head-mounted displays. The audio systems in head-mounted displays can include microphones positioned at or near the entrances of a user's ears to measure the sound produced by the speakers and calibrate the audio system. Current microphones for use in head-mounted displays, such as binaural microphones or microphone arrays embedded in frames of head-mounted devices, have limited sensitivity. For example, typical microphones used in head-mounted devices have difficulty detecting audio pressure waves produced by bone conduction transducers, which generate particle displacements outside the ear in the nanometer or picometer range. To generate pressure waves that can be detected by existing microphones, bone conduction transducers must produce a very loud volume, which is unpleasant for the user.